Ultrasonic Hairstyling Device

ABSTRACT

A device for styling hair includes a wand defining a handle grip surface and a first styling surface spaced from the handle grip surface and a plate defining a second styling surface, the plate being pivotally coupled to the wand to clamp the hair between the first styling surface and the second styling surface. The device further includes a heating element in thermal communication with the first styling surface or the second styling surface to transfer heat to the hair via the first styling surface or the second styling surface, respectively, and an ultrasonic transducer configured to generate ultrasonic vibrations. The ultrasonic transducer includes a horn in contact with the wand or the plate to transmit the ultrasonic vibrations to the hair via the first styling surface or the second styling surface, respectively.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional applicationentitled “Ultrasonic Curling Iron,” filed Oct. 6, 2009, and assignedSer. No. 61/249,074, and U.S. provisional application entitled“Ultrasonic Flat Iron,” filed Oct. 28, 2009, and assigned Ser. No.61/255,657, the entire disclosures of which are hereby expresslyincorporated by reference.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure is generally directed to hairstyling devices, andmore particularly to curling irons and flat irons.

2. Description of Related Art

Traditional techniques for styling hair involve the application of heat.Attempts to style hair faster or create more robust holds have beenbased on increasing the amount of heat applied to the hair. The heatacts upon water molecules contained in the center of the hair.Restructuring the hydrogen bonds between the water molecules allows thehair to retain the desired styling.

Unfortunately, elevated amounts of applied heat tend to dry and damagehair, rendering the hair difficult to style, reducing shine, andultimately resulting in unhealthy hair. Excessive heat can damage theouter layers of the hair, i.e., the cuticle, resulting in split ends.The hair becomes more limp and unable to hold desired styling, once thecuticle and inner shaft of the hair lose the water content that wouldotherwise provide strength.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the disclosure, a device for stylinghair includes a wand defining a handle grip surface and a first stylingsurface spaced from the handle grip surface, a plate defining a secondstyling surface, the plate being pivotally coupled to the wand to clampthe hair between the first styling surface and the second stylingsurface, a heating element in thermal communication with the firststyling surface or the second styling surface to transfer heat to thehair via the first styling surface or the second styling surface,respectively, and an ultrasonic transducer configured to generateultrasonic vibrations. The ultrasonic transducer includes a horn incontact with the wand or the plate to transmit the ultrasonic vibrationsto the hair via the first styling surface or the second styling surface,respectively.

In some cases, the wand is oriented along a longitudinal axis, and theultrasonic transducer is oriented along the longitudinal axis such thatthe ultrasonic vibrations are generated in a direction parallel to thelongitudinal axis. Alternatively or additionally, the ultrasonictransducer is disposed within the wand. The ultrasonic transducer maythen include a horn with a rim in contact with an interior surface ofthe wand that defines an annular interface through which the ultrasonicvibrations travel.

The wand may include a barrel that terminates at an end cap. The platemay be curved to match a curvature of the barrel. The ultrasonictransducer may include a horn in contact with the end cap. Alternativelyor additionally, the barrel may then have a length equal to a wavelengthof the ultrasonic vibrations or a multiple of the wavelength.

In some cases, the device further includes an arm pivotally coupled tothe wand. The plate may be mounted on the arm. Alternatively oradditionally, the first and second styling surfaces may be flat.

The device may include a flat plate mounted on the wand. The flat platemay have a first side that defines the first styling surface and asecond side in contact with the ultrasonic transducer. The ultrasonictransducer may then be oriented in alignment with the wand, and theultrasonic transducer may include a horn adapter to direct theultrasonic vibrations laterally toward the flat plate. The flat platemay have a length equal to a wavelength of the ultrasonic vibrations ora multiple of the wavelength.

In some cases, the wand may include a handle that defines the handlegrip surface and also include a barrel extending from the handle anddefining the first styling surface. The ultrasonic transducer may thenbe disposed in contact with, and external to, the barrel.

In accordance with another aspect of the disclosure, a device forstyling hair includes a first arm defining a first handle grip surface,a second arm pivotally coupled to the first arm and defining a secondhandle grip surface, a first flat plate mounted on the first arm anddefining a first styling surface spaced from the first handle gripsurface, and a second flat plate mounted on the second arm and defininga second styling surface spaced from the second handle grip surface. Thefirst and second flat plates are positioned to clamp the hair betweenthe first and second styling surfaces. The device further includes aheating element in thermal communication with the first flat plate orthe second flat plate to transfer heat to the hair via the first stylingsurface or the second styling surface, and an ultrasonic transducersecured to the first arm and configured to generate ultrasonicvibrations. The ultrasonic transducer includes a horn in contact withthe first flat plate to transmit the ultrasonic vibrations to the hairvia the first styling surface.

The first arm may be oriented along a longitudinal axis, and theultrasonic transducer may be oriented along the longitudinal axis suchthat the ultrasonic vibrations are generated in a direction parallel tothe longitudinal axis.

In some cases, the ultrasonic transducer is disposed within the firstarm. Alternatively or additionally, the ultrasonic transducer isoriented in alignment with the first arm, and the ultrasonic transducerincludes a horn adapter to direct the ultrasonic vibrations laterallytoward the first flat plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects, features, and advantages of the present invention will becomeapparent upon reading the following description in conjunction with thedrawing figures, in which like reference numerals identify like elementsin the figures.

FIG. 1 is a perspective, cutaway view of an exemplary curling ironconstructed in accordance with one or more aspects of the disclosure.

FIG. 2 is a perspective, end view of the curling iron of FIG. 1 todepict an exemplary ultrasonic transducer in greater detail.

FIG. 3 is a perspective view of the ultrasonic transducer of FIG. 2 todepict one or more aspects of the disclosure relating to embodimentshaving a Langevin transducer configuration.

FIG. 4 is a cross-sectional view of a housing of the curling iron shownin FIGS. 1 and 2 taken along the lines 4-4 of FIG. 2 to depict themounting of the ultrasonic transducer of FIGS. 1-3 within the housing inan axial orientation and barrel position in accordance with severalaspects of the disclosure.

FIG. 5 is a schematic diagram of an exemplary drive circuit forcontrolling the operation of the ultrasonic transducer of FIGS. 2-4.

FIG. 6 is a perspective, cutaway view of an exemplary flat ironconstructed in accordance with one or more aspects of the disclosure.

FIG. 7 is a perspective, partial view of an arm of an exemplary flatiron constructed in accordance with another embodiment.

FIG. 8 is a perspective view of an exemplary ultrasonic transducer ofthe flat irons of FIGS. 6 and 7.

FIG. 9 is a cross-sectional view of an arm of a flat iron similar to theview shown in FIG. 4 to depict an exemplary mounting of the ultrasonictransducer of FIG. 8 within the arm.

FIG. 10 is a schematic diagram of another exemplary drive circuit forcontrolling the operation of the ultrasonic transducers of the disclosedhairstyling devices.

FIGS. 11A and 11B are graphical diagrams of data collected during energytransmission testing of the disclosed hairstyling devices.

FIG. 12 is a perspective, end view of another exemplary curling ironconstructed in accordance with an alternative embodiment in which anultrasonic transducer is secured to an exterior barrel surface.

FIG. 13 is a perspective view of an alternative transducer mountingconfiguration in which a modified Langevin transducer transfersvibration energy radially through a flattened horn surface.

DETAILED DESCRIPTION OF THE DISCLOSURE

The disclosure is generally directed to an ultrasonic hair stylingdevice that transmits ultrasonic vibrations to the hair to reduce theamount of heat applied for styling. The disclosed devices generallyimprove hairstyling by decreasing the time and temperature level of theapplied heat, thereby improving the overall health of the hair,increasing shine, and improving styling hold. In this way, users of thedisclosed devices can style hair faster and create longer-lasting holdswithout having to resort to the application of more heat. Instead ofconventional styling heat levels of 400-450° F., use of the discloseddevices has effectively styled hair at temperature levels around about250° F. to about 350° F.

The ultrasonic vibrations generally apply energy to the hair via thestyling elements or surfaces in contact with the hair. The energy fromthe ultrasonic vibrations then adds to the energy applied by the heatsuch that the total energy reaches a level appropriate for styling. Theenergy from the ultrasonic vibrations also results in improved heatdistribution in the styling elements or surfaces, which may also helpreduce the time needed to achieve and set the desired styling. Inhairstyling devices involving wet-to-dry operation, the ultrasonicvibrations lead to faster drying and, thus, lower amounts of appliedheat. For these reasons, the likelihood or risk of damage to the hairdecreases.

Although described below in connection with curling irons and flatirons, the ultrasonic vibrations may be useful in connection with avariety of hair styling tools or techniques. Thus, the disclosed hairstyling devices are not limited to curling irons or flat irons.Nonetheless, in some cases, the ultrasonic vibrations may be transferredwhile the hair is clamped or otherwise fixed between styling tools orelements. In this way, contact between the vibrating elements of thedisclosed devices in the hair is ensured.

Turning to the drawing figures, FIG. 1 depicts a curling iron 20 havingan elongate housing 22. A base portion of the housing 22 forms a handle24 from which a barrel 26 of the housing 22 extends. The handle 24provides a handle grip surface 28 for an operator of the curling iron 20to grasp during use. The barrel 26 provides a styling surface 30 spacedfrom the handle grip surface 28 to avoid or minimize unwanted usercontact with the styling surface 30. The styling surface 30 is generallyconfigured for winding hair to be styled around the barrel 26 to formcurls or other styling effects. To that end, the elongate housing 22 andeach portion thereof may be generally cylindrically shaped, although thehandle 24 and the barrel 26 may be shaped otherwise and, moreover, neednot be similarly shaped. The handle 24 and the barrel 26 are configuredsuch that the housing 22 is shaped as a wand or an arm.

The handle 24 and the barrel 26 may be integrally formed to any desiredextent. The handle 24, for instance, may include a rubberized, plastic,or other grip (not shown) mounted upon an extension of the barrel 26. Inother cases, one or both of the portions of the elongate housing 22 maybe formed via interlocking or interconnected half- or other shells. Forexample, the handle 24 may include a molded, two-piece constructionconsisting of two matching, half-cylinder plastic covers secured to oneanother via one or more screw or other fasteners. These and other partsof the handle 24 may be constructed of a variety of materials other thanplastics, including stainless steel. The barrel 26 may include one ormore components constructed of stainless steel, iron, aluminum, or otherthermally conductive materials. In some cases, the handle 24 and thebarrel 26 are discrete structures connected to one another via one ormore fasteners, one or more snap-fit connectors, or some other couplingmechanism. Alternatively, the handle 24 may be configured as a sleevethat fits over a tube or other housing that runs the length of thedevice to also form the barrel 26.

The handle 24 includes a number of user interface or control elements.To this end, the handle 24 may have a non-circular cross-sectionalshape. The example shown, for instance, has a longitudinal ridge 31 thatruns the entire length of the handle 24. The ridge 31 presents a panelor other section of the grip surface 28 for the user interface orcontrol elements. The ridge 31 and other projections may also improvethe grip surface 28. In other cases, the handle 24 may have an oval orother non-circular cross-sectional shape to configure the grip surface28 in a desired manner. Similarly, the barrel 26 need not have acircular cross-sectional shape as shown in the event that, for instance,a different curl or other styling effect is desired.

Both the handle 24 and the barrel 26 are configured as hollow tubes toaccommodate a number of functional elements, such as electricalcomponents and circuitry. These components generally support theoperation of the curling iron 20, which includes ultrasonic vibration asdescribed below. In this example, the handle 24 houses a circuit board32 shaped as an elongate strip oriented lengthwise and mounted withinthe handle 24 via one or more screw or other fasteners. The barrel 26,in turn, houses one or more heating elements 34 and an ultrasonictransducer 36. The heating elements 34 are generally disposed within thebarrel 26 in thermal communication with the styling surface 30 totransfer heat to the hair wound around the barrel 26. In this example,each heating element 34 includes a thermally conductive strip 38disposed and extending along an interior wall of the barrel 26. Eachstrip 38 may have any desired shape, including, for instance, a flat orcurved plate. Both the heating elements 34 and the ultrasonic transducer36 are generally oriented lengthwise within the barrel 26.

Each heating element 34 may be conventionally constructed andconfigured. Suitable heating element materials include ceramics andmetals. In this example, each heating element 34 includes an elongate,flat, ceramic plate disposed upon a flat or other mount inside thebarrel 26. Each mount may be constructed of a heat conductive materialto encourage the transfer of heat from the heating element 34 to thestyling surface 30 of the barrel 26. The barrel 26 in this case has apair of opposing heating elements positioned lengthwise within thebarrel 26. Each heating element 34 may run the length of the barrel 26or any desired segment thereof. In this example, each heating element 34extends from an inner end of the barrel 26 to the electronic transducer36, stopping short of the outer end of the barrel 26 as shown. Anynumber of heating elements 34 may be disposed within the barrel 26 at avariety of locations, including those that reach the outer end of thebarrel 26 as with, for instance, the embodiment described below. Onepotential advantage of the disclosed hair styling devices, however, isthat the number, size, or intensity of the heating elements 34 may bereduced as a result of the application of ultrasonic vibrations, asdescribed below. Nonetheless, the disclosed hair styling devices maystill include a conventional amount of heating capacity to provide theoperator with various operational options, including a non-ultrasonicoption. In these and other ways, the curling iron 20, for instance, maybe configured to present a range of possible heating levels to theoperator to accommodate different hairstyling requirements arising from,for instance, differing hair thickness.

The curling iron 20 also includes a clip assembly 40 pivotally securedto the elongate housing 22. The clip assembly 40 may include one or moresprings or other elastic elements to bias the clip assembly 40 towardthe barrel 26 to thereby clamp and hold the hair in position between thestyling surface 30 of the barrel 26 and a plate 42 of the clip assembly40. The plate 42 extends lengthwise along the barrel 26 and has astyling surface 44 on an inward facing side. The plate 42 is generallycapable of moving the styling surface 44 into a position facing oropposite from the styling surface 30 of the barrel 26. The barrel 26 andthe plate 42 may be configured so that the shapes of the stylingsurfaces 30 and 44 are matching or complementary. For instance, theplate 42 may be curved to an extent to match the curvature of the barrel26.

In this example, the plate 42 is pivotally coupled to the elongatehousing 22 via a pivot link 46 of the clip assembly 40. The pivot link46 has one or more ends that terminate at a respective pivot joint orhinge 48 at which the clip assembly 40 is secured to the elongatehousing 22. In this example, the clip assembly 40 has two diametricallyopposed pivot joints 48 at an inner or proximate end 50 of the barrel26. Each pivot joint 48 includes a pin, bolt, or other pivot element 52that passes through the pivot link 46 and the barrel 26. The pivot link46 generally extends laterally outward from the barrel 26 to form alever 54, which may, in turn, include a grip surface 56 to facilitateoperator engagement during operation. The manner in which the clipassembly 40 is pivotally coupled may vary considerably. For instance, insome cases, the clip assembly 40 is secured to the handle 24.

The shape, construction, and other characteristics of the handle 24, thebarrel 26, and the clip assembly 40 may vary considerably from theexample shown. A variety of different configurations and constructionsare well suited for use with the ultrasonic features of the disclosedhairstyling devices.

The circuit board 32 includes a number of circuit elements 58 to controleach heating element 34 and the ultrasonic transducer 36. The circuitryresponsible for controlling the heating and ultrasonic vibratingfunctions may be integrated to any desired extent. In some cases, aseparate circuit board may be disposed within the elongate housing 22 tohandle one of the two functions alone. In any event, the circuitelements 58 may be disposed in a location within the elongate housing 22(e.g., near a base end of the handle 24) to avoid the heat generated bythe heating elements 34. Because one or more of the circuit elements 58may also constitute sources of heat, the circuit elements 58 may benonetheless configured for operation in an elevated temperatureenvironment. Temperature levels within the housing 22 may exceed normaloperating temperatures even though the circuit elements 58 are spacedfrom the heating elements 34. To help dissipate heat, one or more of thecircuit elements 58 may include a heat sink 60. For example, one or morecopper elements may be disposed upon a circuit board 32 or a respectiveone of the circuit elements 58. In some cases, the curling iron 20 mayinclude a barrier, divider, wall, or other element within the housing 22to block the transmission of heat from the barrel 26 to the componentswithin the handle 24.

The circuit board 32 is coupled to a power source via a power cord 62.In other examples, the circuit board 32 is coupled to a battery or otherportable power source, which may be rechargeable via, for instance, thepower cord 62. The circuit board 32 is also coupled to one or morecontrol or input elements 64. One or more of the control elements 64 maybe directed to activating and deactivating the curling iron 20 or one ormore operational features thereof, including ultrasonic vibration. Othercontrol elements 64 may be directed to selecting or determiningoperational parameters, such as heat level and ultrasonic vibration. Forinstance, an operator may be given an opportunity to adjust the heatlevel to a lower temperature when the ultrasonic vibration feature isactivated. In other cases, the heat level is automatically reduced uponactivation of the ultrasonic vibration feature. More generally, anoperator may adjust the temperature level to customize the curling iron20 for personal use requirements or preferences.

The positioning, structural configuration, and other physicalcharacteristics of the electrical and circuit-related components of thecurling iron 20 may also vary considerably from the example shown. Forexample, circuit elements may be disposed on more than one circuit boardor otherwise spaced apart to improve heat dissipation. Details regardingthe electrical characteristics of the circuit-related components areprovided below.

As described below, the ultrasonic transducer 36 is generally configuredto generate ultrasonic vibrations to improve and facilitate hairstylingthrough lower levels of applied heat. In this example, the ultrasonictransducer 36 includes an assembly of components disposed within thebarrel 26. In that way, the vibrations generated by the transducer 36are transmitted through the barrel 26 to the styling surface 30, atwhich point the vibrations are, in turn, transmitted to the hair incontact therewith. To that end, the ultrasonic transducer 36 isgenerally disposed in a position that allows the vibrations to betransmitted to the styling surface 30 and, ultimately, to the hair beingstyled. In this example, the transducer 36 is mounted or orientedlengthwise along a longitudinal axis of the barrel 26. The longitudinalaxes of the barrel 26 and the transducer 36 are aligned such that theultrasonic vibrations are generated in a direction parallel to thelongitudinal axis. This transducer orientation allows the size andlength of the transducer 36 to be maximized in the limited spaceavailable within the barrel 26. However, as shown with the examplesdescribed below, the location and orientation of the transducer 36 mayvary, including, for instance, non-axial orientation involving a radialmount.

With reference now to a FIG. 2, a partial view of the curling iron 20 isshown to depict one possible location of the ultrasonic transducer ingreater detail. In this example, the ultrasonic transducer 36 isdisposed adjacent an end cap or plug 66 of the barrel 26. The transducer36 is shown in phantom to depict how a front face 68 of the ultrasonictransducer 36 is in contact with the end cap 66. To this end, thetransducer 36 is positioned at an outer or distal end 69 of the barrel26 such that the front face 68 abuts the end cap 66. As describedfurther below, the transducer 36 is also positioned, shaped and sizedfor further contact with the barrel 26. Generally speaking, the width ofthe transducer 36 may result in contact with the longitudinal wall(s) ofthe barrel 26. In this case, the transducer 36 is configured such thatan inner longitudinal wall of the barrel 26 is contacted by a rim 70 ofthe transducer 36 to form an annular interface at the front face 68. Inthis way, the vibrations generated by the transducer 36 may betransmitted to the styling surface 30 via both the end cap 66 and theannular interface with the barrel 26. As also shown in FIG. 3, the rim70 extends along the longitudinal axis of the transducer 36 to form acylindrical surface or band for the annular interface with the barrel26.

The ultrasonic transducer 36 may be disposed at other locations withinthe elongate housing 22. For example, the transducer 36 may be disposedat the inner end 50 of the barrel 26. In that case, the front face 68 ofthe transducer 36 may again be adjacent another end cap or other face(not shown) to maximize the surface area of the interface between thetransducer 36 and the barrel 26. In such cases, the transducer 36 maynot extend the entire width of the barrel 26 so as to allow electricalconnections and other elements to pass by the transducer 36 to reach theheating elements 34 (FIG. 1). To that end, the rim 70 may include a gapor spacing to act as a pass-through for wiring, etc. In other cases, theannual interface may be the sole transmission conduit for the ultrasonicvibrations. If the transducer 36 is disposed not at either end of thebarrel 26, but rather at a point therebetween, the contact between therim 70 and the inner surface of the barrel 26 may form the onlytransmission conduit between the barrel 26 and the transducer 36 for theultrasonic vibrations. Still other cases may position the transducer 36within the handle 24, at a wall or other element separating the handle24 and the barrel 26, or at any other location within the housing 22.

The ultrasonic transducer 36 may be secured within the elongate housing22 via an adhesive layer or film 72 between the rim 70 and the innersurface of the barrel 26 (also shown in FIG. 4). A variety of adhesivematerials are well suited for the mounting, including, for instance,those products commercially available from 3M Corporation, which may beapplied to the inner surface(s) of the barrel 26. The 3M adhesiveproducts may be configured as a pressure-sensitive film. The adhesivematerial is generally insensitive to the elevated heat levels within thebarrel 26. The material from 3M Corporation is rated for use at up to550 F. degrees. The adhesive layer 72 generally addresses the challengeof securing the transducer 36 without dampening or otherwise interferingwith the transmission of the ultrasonic vibrations. To that end, theadhesive layer 72 may be configured and applied as a thin film. In somecases, the ultrasonic transducer 36 is alternatively or additionallyinserted into the barrel 26 or, more generally, the elongate housing 22in a pressure-fit arrangement. In that way, the ultrasonic vibrations donot experience a significant barrier to transmission through the annularor other interface between the transducer 36 and the styling surface 30.Furthermore, an adhesive layer need not be applied between thetransducer 36 and the end cap 66, thereby allowing the vibrations topass through that interface without adhesive-related dissipation.

FIG. 3 shows the ultrasonic transducer 36 in greater detail. Thetransducer 36 generally includes a horn 80, a piezoelectric section 82,and a reflector 84. In this example, these stages of the transducer 36are arranged in the Langevin configuration. The horn 80 is generallyconfigured as a front-end stage to transmit the ultrasonic vibrationsgenerated in the piezoelectric section 82. To that end, the horn 80 isshaped and otherwise configured for efficient transfer and transmissionof the vibrations. In this example, the horn 80 is shaped as a truncatedcone (or frustum) such that a tapered section of increasing diameterextends forward from the piezoelectric section 82. The horn 80terminates in a front face 86, which may be flat to maximize contactwith the end cap 66, the barrel 26 (FIG. 1) or other component of thehousing 22. The reflector 84 is positioned behind the piezoelectricsection 82 as a back-end stage of the transducer 36 generally designedto reflect or direct the ultrasonic vibrations in the desiredtransmission direction through the front end stage (e.g., through thefront face 86 of the horn 80 toward the barrel 26 or the housing 22).The reflector 84 is sized and weighted to that end. For example, a solidcylinder of stainless steel or other dense material may be used as thereflector 84. The reflector 84 is set at a distance that is a directmultiple of the wavelength of the vibrations so that wave reflectionswill be in phase with the waves emanating from the piezoelectric section82.

The piezoelectric section 82 is disposed between the front- and back-endstages of the transducer 36. The piezoelectric section 82 includes a setof piezoelectric discs 88 arranged in a stack. Each disc 88 may be madeof Lead zirconate titanate (PZT) or other piezoelectric ceramic(s) orother material(s) with the piezoelectric property of changing shape uponthe application of an electric field. PZT and other ceramic materialsare useful in the curling iron context due to heat compatibility, as theheating elements 34 are conventionally raised to temperature levels ofapproximately 400-450° F. for hairstyling (or 250-350° F. with thebenefit of ultrasonic vibration as described herein). The piezoelectricdiscs 88 as well as the transducer 36 are commercially available fromSunnytec Electronics Co. Ltd. (Taiwan). The disc stack is generallyconfigured so that the vibrations generated by the discs 88 are in phasefor constructive amplification. In this case, the stack includes fourdiscs 88 oriented axially, or longitudinally, within the housing 22(FIG. 1). Other disc arrangements are possible, but an even number ofdiscs is useful for maintaining a constructive interference scenario forthe vibrations. Electrodes 90 are positioned on each side of the discs88 to apply an excitation or drive signal to each disc 88. Theexcitation signal may include an AC component with, for instance, a 160Volt peak-to-peak amplitude. The amplitude may be increased to amplifythe strength of the resulting vibrations. Amplitudes as high as 320 Vpeak-to-peak have been found to be suitable. The number of piezoelectricdiscs 88 may be increased to accommodate the higher amplitudes. Othercharacteristics of the excitation signal, including frequency, may beestablished through pulse density modulation. The frequency (oreffective frequency) of the excitation signal generally determines thefrequency of the vibrations generated by the transducer 36. As a result,the excitation signal frequency is generally selected in accordance withthe desired vibration frequency of the transducer 36.

Positive and negative pairs of the electrodes 90 are reached viaU-shaped contacts 92, which generally run along the stack lengthwisebefore bending radially inward toward the electrodes 90. Each contact92, in turn, is connected to wiring (not shown) that leads to thecircuit board 32 (FIG. 1). The contacts 92 may be integrally formed withthe electrodes 90. More generally, each contact 92 may be configured asa plate having a flat section. In some cases, the flat section of theplate may provide a stable surface for mounting the transducer 36 withinthe housing 22 (FIG. 1).

The three stages of the transducer 36 are secured to one another by abolt or other fastener 94 that extends axially forward from thereflector 84 through the discs 88 of the piezoelectric stage 82 to reachthe horn 80. To that end, each disc 88 and each electrode 90 may have ahole (not shown) formed in the center thereof to allow the bolt 94 topass through. The bolt 94 may have a threaded end 96 configured toengage a matching threaded opening (not shown) in the horn 80. The bolt94 may be welded or otherwise fixed to the reflector 84 at its otherend. In some cases, the bolt 94 may be integrally formed with thereflector 84. During assembly of the transducer 36, the reflector 84 isrotated relative to the horn 80 for compression of the stages of thetransducer 36. The horn 80 and the reflector 84 include opposed pairs offlattened sections 98, 100, respectively, to allow a wrench or othertool to help tighten the assembly to reach a suitable level ofcompression.

FIG. 4 shows the exemplary axial mounting of the transducer 36 withinthe outer end 69 of the barrel 26 in greater detail. The front face 68of the horn 80 is disposed along, and in contact with, the end cap 66 ofthe barrel 26. The rim 70 is sized so that the annular interface andcontact between the transducer 36 and the barrel 26 spans the entirecircumference of an inner surface 102 of the barrel 26. In this case,the adhesive layer 72 is, in fact, limited to the annular interface suchthat the vibrations passing through the front face/end cap interfaceavoid any dampening or suppression that would otherwise arise from thepresence of an intermediate adhesive layer. The adhesive layer 72 mayalso be used to secure the end cap 66 in place at the outer end 69 ofthe barrel 26. Additional mounting hardware (not shown) may be disposedwithin the barrel 26 to hold the transducer 36 in place.

The heating elements 34 in this example are disposed along the innersurface 102 of the barrel 26. However, the heating elements 34 need notbe curved to match the curvature of the barrel 26 and, thus, need not bedisposed in contact with the inner surface 102 across their entire widthor length. Instead, the heating elements 34 are more generally disposedalong the barrel 26 at a radial position outward of the transducer 36and either directly or indirectly coupled to the inner surface 102. Anindirect coupling may include heat-conductive mounting hardware (notshown) that establishes the transmission of heat from the elements 34 tothe inner surface 102 and, from there, through the barrel 26 to thestyling surface 30 opposite the inner surface 102.

The transducer 36 has an overall axial length L_(T) and a horn lengthL_(H), as defined in FIG. 4. Generally speaking, these length dimensionsare selected to maximize the generation and transmission of ultrasonicvibrations through resonance of the transducer 36. To that end, thedimensions L_(T) and L_(H) may be about λ/2 and λ/4, respectively, whereλ is the wavelength of the ultrasonic vibrations generated by thetransducer 36. When these length conditions are met (or approximatelymet), the transducer 36 may be driven to an oscillation mode having anode (where vibration amplitudes are at or near a minimum) at a rearface 104 of the reflector 84 and an anti-node (where vibrationamplitudes are at or near a maximum) at the front face 68 of the horn80. Under these conditions, the vibrations generated by the transducer36 form standing waves within the transducer 36, effectively reflectingfrom the back-stage reflector 84 and combining in phase with thosetraveling forward to the horn 80 to reach the front face 68 at peakstrength. In one example, the overall axial length L_(T) is 56 mm andthe horn length L_(H) is 17 mm.

Notwithstanding the foregoing, the diameter of the barrel 26 may presentchallenges for the design and mounting of the transducer 36 and therebycause a deviation from the ideal λ/4 configuration. In some cases, thediameter of the rim 70 of the horn 80 may be limited by the diameter ofthe barrel 26. As a result, the length of the horn 80 may be shorterthan the optimal length in order to achieve resonant operation with theother stages of the transducer 36. In one example with a 1.5″ diameterbarrel, the horn 80 is shorter than the optimal length to ensure thatthe horn 80 resonates at the same frequency as the piezoelectric stage.The shorter horn length also helps to maintain a proper massdifferential between the reflector and horn stages in the interest ofensuring that the vibrations are directed toward the horn.

With the horn-shaped (or frustoconical) transducer configuration shownin FIGS. 1-4, the lengths may be selected for operation at a number ofnatural resonant frequencies between about 20 kHz and about 1 MHz. Insome cases, the piezoelectric discs 88 may be configured such that theoperating (i.e., vibration) frequency exceeds about 50 kHz. Thevibration frequency for one exemplary embodiment involving thehorn-shaped transducer configuration was above about 60 kHz and, in somecases, about 87.5 kHz. The vibration frequency may be selected inaccordance with other operational parameters, including powerconsumption, temperature level, weight, and size. Differences in barrelgeometry and size may result in different resonant frequencies. Thus,the foregoing operational frequencies are exemplary in nature due to theexemplary nature of the transducer assembly 36, which has a front facediameter of 29.5 mm, a disc/reflector diameter 15.04 mm, and a reflectorlength of 25.44 mm.

During operation, the vibrations generated by the piezoelectric discs 88travel axially forward to the horn 80. Once at the horn 80, thevibrations travel further forward to transmit energy to the end cap 66via the front face 68. The vibrations of the horn 80 also spreadradially to transfer energy to the barrel 26 via the annular interfacebetween the rim 70 and the inner surface 102 of the barrel. Throughthese transmission paths, the ultrasonic energy eventually reaches thehair clamped between the styling surface 30 and the styling surface 44(FIG. 1). There, the ultrasonic energy is applied to the moistureentrapped in the medulla of the hair.

The transmission of ultrasonic energy improves the styling of the hairby facilitating heat transfer within the barrel 26 and by acceleratingthe restructuring of hydrogen bonds with the hair. On the one hand, theultrasonic vibrations result in more efficient transfer of heat from theheating elements 34 to the hair through excitation of the moleculeswithin the barrel 26. The excitation of the barrel molecules lowers theheat transfer resistance of the barrel 26. More effective transmissionof heat through the barrel 26 lowers the possibility of undesirable hotspots along the barrel, which could otherwise damage hair. Moreeffective heat transmission also lowers the overall heating required toraise the temperature of areas along the barrel 26 other than the hotspots. The general result is more uniform distribution of heat along thebarrel 26. Turning to the effects on the hair itself, the vibrationsapply energy to the hydrogen bonds between the water molecules in themedulla of the hair. To style hair, these weak electrochemical bonds arebroken so that the molecular bonds can be reformed with the molecules indifferent positions. The ultrasonic energy supplies part of the totalamount of energy required to break the bonds. As a consequence, lessenergy is required from the heat, which ultimately helps to preventdamage to the hair follicle resulting from the heat. For all of thesereasons, the hair can be styled faster, which, in turn, lowers the totalamount of heat applied to the hair, thereby reducing the possibility fordamage.

With reference now to FIG. 5, an exemplary drive circuit 110 for theultrasonic transducer 36 (FIGS. 1-4) includes several components forcontrolling and generating the drive signal. The circuit 110 as showndoes not include any components for controlling or powering the heatingelements 34 (FIGS. 1 and 4). However, the drive and heating controlcircuitry may be integrated to any desired extent. For example, theinput control parameters for activation/deactivation, heating levels(e.g., low, medium and high), and ultrasonic operation may be deliveredto both the drive and heating control circuitry for integratedoperation. The circuit 110 includes an EMI line filter 112, which isoptional depending on whether interference on the AC power line providedto the curling iron 20 is considered a problem. In some cases, suchinterference or other noise may affect the operation of the circuit 110to an extent that the drive signal includes harmonic or other undesiredfrequency components. The operation of the curling iron 20 may, as aresult, become less efficient (e.g., through diversion of power awayfrom the effective frequencies). Alternatively or additionally, thepresence of undesired components in the drive signal may lead tovibration at undesired frequencies, such as audible frequencies. In thisexample, the filtered AC line power is provided to a high voltageAC-to-DC converter 114 and a low voltage AC-to-DC converter 116. Thehigh voltage converter 114 includes a bridge rectifier 118 and capacitorC3 configured to generate a high DC voltage input V_hv suitable for usein generating the drive signal. The low voltage converter 116 includes abridge rectifier 120 and a voltage regulating network 122 to generate anoutput suitable for use as a power supply Vcc for the logic devices ofthe circuit 110. In this case, the network 122 includes a Zener diode D3to lower the output of the bridge rectifier 120 and a regulator 124 togenerate a stable power supply voltage Vcc of 12 Volts. The regulator124 may include one of the linear regulators commercially available fromNational Semiconductor Corporation associated with product numberLM78L12.

The exemplary drive circuit 110 is configured as a full H-bridge drivercircuit. Other control circuits may instead include otherself-oscillating, switched power supplies, such as a half bridge drivercircuit. Still other alternatives may be based on a driven circuitconfiguration in which, for instance, a crystal is used to set anoperating frequency. In this case, the power supply voltage Vcc isprovided to a timer 126 configured and set in a stable mode for use asan oscillator. To that end, the timer 126 is coupled to a resistor R12to set the frequency and duty cycle parameters. A commercially availabletimer suitable for use as the timer 126 may be obtained from NationalSemiconductor Corporation associated with product number LM555. Theoscillating output of the timer 126 may be provided to a divider 128configured to, for instance, reduce the duty cycle by 50%. A full-bridgedriver 130 receives the oscillating signal to develop switch controlsignals for two full-bridge switch circuit pairs 132. In operation, theswitch circuit pairs 132 are selectively activated in accordance withthe switch control signals to generate an AC output drive signal basedon the high DC voltage input V_hv and apply the signal to the ultrasonictransducer (FIGS. 1-4) to drive the transducer 36 for generation of theultrasonic vibrations.

One or more of the above-identified integrated circuit chips or circuitcomponents may be coupled to a heat sink. The heat sink(s) help maintainthe operating temperatures of the chips and components to levels withina desired operating temperature range. The heat generated by the heatingelements 34 (FIG. 1) as well as the heat generated by the operation ofthe drive circuit 110 itself may lead to temperatures within the housing22 (FIG. 1) that would otherwise be elevated to undesirable levels. Thatsaid, the operation of the oscillator and other AC-related components ofthe circuit 110 has been found to remain functional despite the heatlevels reached during operation. For instance, the operatingtemperatures may result in a slight shift in the frequency of the drivesignal. In some cases, the frequency shift may be inconsequential, whilein other cases other parameters can be adjusted to compensate for theshift.

In some cases, one or more circuit elements may be incorporated into thedrive circuit 110 to address spurious vibration modes or other undesiredvibrations. For example, a potentiometer may be added to preventundesirable harmonic frequencies of the drive signal frequency fromreaching the transducer. Otherwise, the harmonic frequencies may beaudible to the operator of the curling iron or the operator's pets. Thepotentiometer may be configured to modify the duty cycle of theoscillator output.

The drive signal generated by the circuit 110 may have a peak-to-peakamplitude of about 160 Volts. With the full H-bridge driver is used, theamplitude may be increased to as high as 320 Volts, in which case thenumber of piezoelectric discs may be increased accordingly toaccommodate the higher amplitude. Thus, the amplitude may fall withinthe range of about 160 Volts to about 320 Volts for some embodiments.With these amplitudes, the drive signal may, for instance, provide10-100 Watts of power to the ultrasonic transducer. The amplitudes mayexceed that range in some cases (e.g., transformer-based circuits) todeliver more energy to the hair and the barrel, although at the cost ofincreased component size and weight.

The drive circuit 110 does not include a transformer to generate thehigh AC drive voltage, despite the prevalence of transformers inultrasonic drive circuits. A transformer would add significant andundesirable amounts of size and weight to the hairstyling device. Whilethe non-transformer drive circuit described above may be limited tolower drive voltage amplitudes, that factor can be offset by theselection of the drive frequency and optimal tuning of the transducerhorn. For example, the transducer geometry may be adjusted and analyzedto operate at a natural resonant frequency of the transducer. An FEApackage was used to analyze and determine the natural resonantfrequencies. Geometric adjustments then led to an operational frequencyclose to the natural resonant frequency of the transducer and the drivefrequency of the piezoelectric discs. The mounting of the transducer mayalso lead to improved transfer of the axial horn vibrations to thebarrel. Notwithstanding the foregoing, all component values shown inFIG. 5 are exemplary in nature in multiple respects, including, forinstance, that the component values are directed to generating a drivesignal with a frequency of 40 kHz.

Turning to FIG. 6, the benefits of ultrasonic vibration are nowdescribed in connection with another exemplary hairstyling device. Likethe curling iron 20 described above, a flat iron 140 is configured totransmit ultrasonic energy to the hair being styled via one or morestyling surfaces. In this case, the styling surface(s) are flat for hairstraightening rather than curved for hair curling. Differences relatingto ultrasonic vibration between the hairstyling devices are driven bythe device geometries. For example, some of the differences relate tothe direction in which the vibrations propagate. With flat and othernon-circular device geometries, the vibrations may travel laterally,longitudinally, or any combination thereof. These and other differencesand similarities are described further below.

The flat iron 140 includes an elongate housing 142 that has severalcomponents in common with the housing 22 described above. The housing142 similarly defines a handle grip surface 144 and a styling surface146 spaced from the handle grip surface 144. A plate 148 is alsopivotally coupled to the housing 142 to clamp the hair between a stylingsurface 149 of the plate 148 and the styling surface 146. In this case,however, the plate 148 is carried by another elongate housing 150(rather than a clip), and the styling surface 146 is an exterior face ofanother plate 152 carried by the housing 142. The housing 150 isconfigured as a pivoting arm (or wand) with a proximal, linked end 154upon which a pivot joint 156 is mounted for coupling with a proximal,linked end 158 of the pivoting arm (or wand) of the housing 142. The twowands or arms extend outward from the linked ends to define alongitudinal axis of each housing 142, 150. The plates 148 and 152 aredisposed at distal, free ends 160 and 162 of the housing arms,respectively, at locations disposing the styling surfaces 146, 149opposite one another. The housing 150 also has a handle grip surface 164so that an operator can grasp the two wand-shaped housings 142, 150 tobring the styling surfaces 146, 149 toward one another. In this manner,the plates 148, 152 can act as pressure plates to apply pressure to thehair to be styled therebetween. The pivot joint 156 is spring-loaded tobias the flat iron 140 open when no inward force is applied to thehandle grip surfaces 144, 164.

Each plate 148, 152 may be fixedly or otherwise mounted within a recess,notch, or other hole in its respective housing. The plates may be madefrom stainless steel, aluminum, copper, or any other suitably thermalconductive material. Each housing 142, 150 may be made from stainlesssteel, aluminum, plastic, or any other desired material.

The flat iron 140 also includes a power cord 166 for delivery of powerto one or more control circuits (not shown) disposed within one or bothof the housings 142, 150. In this case, a control circuit may bedisposed within the housing 142 in proximity to a control panel 168 thatincludes user interface elements 170, 172 for operator control of theflat iron 140. The control panel 168 may be used to activate anddeactivate an ultrasonic vibration feature of the flat iron 140 providedby an ultrasonic transducer 174. The control panel 168 may also be usedto select a temperature level or other operational parameters. Heat isapplied to the hair clamped between the styling surfaces 146, 149 viaone or more heating elements 176 in thermal communication with arespective one of the surfaces 146, 149. Each heating element 176 may beconfigured as a flat plate secured to an interior side of one of theplates 148, 152. In this case, the housing 142 is shown with one of theheating elements 176, although, in other cases, the other housing 150may contain the sole (or an additional) heating element secured to theplate 148.

The ultrasonic transducer 174 is again configured as an assembly ofsections or stages disposed within a hollow interior space of a wand orarm of the hairstyling device. The transducer 174 is generallyconfigured to generate ultrasonic vibrations to facilitate energytransmission with one or both of the pressure plates 148, 152 and totransfer vibration energy to the hair clamped therebetween. However, inthis case, the interior space provided by each housing 142, 150 of theflat iron 140 may not be sufficiently large or appropriately shaped tomount the Langevin transducer described above in a manner that disposesthe front face of the horn in contact with a matching surface within thehousing. However, it may remain beneficial to orient the transducer 174axially within the housing, with the longitudinal axes of the transducer174 and the housing aligned. Consequently, the transducer 174 in thedepicted example is configured with a horn 178 having an adapter thattranslates the longitudinal, axial vibration into vibration in a lateraldirection toward one of the plate 152. To that end, the horn 178includes an L- or elbow-shaped head 180 that projects forward from acylindrical section of the horn 178 adjacent a piezoelectric stage 182.After extending forward, the L-shaped head 180 projects laterallydownward to place an outer end 183 in contact with an interior surface184 of the plate 152. The remainder of the transducer 174 may rest upon,and be secured to the heating element 176 or other surface or componentwithin the housing 142. A similarly mounted transducer may be housedwithin the housing 150 for transmission of ultrasonic vibrations throughthe plate 148. In operation, the vibration mode causes the head 180 tomove laterally (as opposed to axially) toward and away from the plate152. The transducer 174 thus vibrates along a hammer-like motion path.

Despite the directional translation of the vibration propagationachieved by the head 180, the profile of the flat iron wands or armsmay, in some cases, be too thin to mount the transducer 174 within thehousing. The thickness of the heating element 176 may also be a factor.Part of the problem may also arise from a transducer selected orconfigured for a desired resonant frequency, power capacity, or otheroperational parameter that ends up being too large for the housing.

FIG. 7 depicts one optional solution in which a flat iron wand or arm190 has a main housing 192 and a transducer cover 194. The main housing192 may be configured in a similar manner to those described above, withthe exception of a hole on an outward facing side 196 from which thetransducer cover 194 flares or extends laterally outward. In this way,the transducer cover 194 defines a secondary housing or enclosure thatprovides additional space for an interior transducer mount. Thetransducer (not shown) may have a configuration like any of thetransducers described herein, including the Langevin configuration shownin FIG. 3. Thus, the transducer may be mounted in longitudinal alignmentas described above, with or without the adapter translation that allowsthe transducer to meet the interior surface of a plate 198. However,with sufficient additional space under the cover 194, the transducer maybe mounted laterally with the front face of an adapter-free Langevinhorn in contact with the interior surface of the plate 198, such thatthe longitudinal axis of the transducer is orthogonal to thelongitudinal axis of the main housing 192. Thus, the main housing 192and the transducer cover 194 may be shaped as desired and, furthermore,be integrally formed to any desired extent, including, for instance, asa unitary molded component.

With reference now to FIGS. 8 and 9, a Langevin transducer 200 with avibration-translating horn adapter 202 is shown in greater detail.Starting from a back end, the transducer 200 has a reflector stage 204in compression fit with a piezoelectric stage 206 and a horn stage 208.The reflector and piezoelectric stages 204, 206 may be configured in amanner similar to the example described above. The horn stage 208 mayhave a cylindrical section 210 having an inner end 212 adjacent thepiezoelectric stage 206 and an outer end 214 adjacent the horn adapter202. The outer end 214 may have a flat face from which an axiallyoriented arm 216 of the horn adapter 202 extends forward. The arm 216may be integrally formed with the cylindrical section 210 to any desiredextent or, alternatively, be attached to the cylindrical section 210 viaa variety of different attachment techniques (e.g., welding, adhesive,etc.). The arm 216 projects outward until reaching a corner or shoulder218 of the adapter 202, at which point another arm 220 projectslaterally downward. The arms 216, 220 need not be rectilinear as shown,and may be solid, hollow, or any combination thereof.

As shown in FIG. 9, a bottom or downward facing surface 222 of the arm220 is disposed in contact with an inner face 224 of a styling plate226. The face 224 is exposed for such contact between a heating element227 and an inward face 228 of a housing 230. The horn adapter 202 may besecured to the inner face 224 via an adhesive layer or film.Alternatively or additionally, the adapter 202 may be fixed to the plate226 via welding or other attachment techniques. In some cases, the hornadapter 202 is fixed in place by mounting hardware that engages thehousing 230 or the heating element 227. For example, the mountinghardware may engage electrode plates 232 of the piezoelectric stage 206.The adapter 202 may be optionally attached to an inner surface of theheating element 227 or other component or surface within the housing228.

The overall length L_(T) and horn length L_(H) dimensions of thetransducer 200 may be selected in accordance with the above-describedconsiderations. The horn length includes the combined length of thecylindrical section 210 and the adapter 202. The length of the reflectorstage 204 is noted as L_(R) and may be a direct multiple of thewavelength in the interest of constructive interference (as is the casewith the above-described example).

As described above, the transducer 200 may be configured with dimensionsoffset from the desired lengths in order to ensure that the hornresonates at substantially the same frequency as the ceramic discs ofthe piezoelectric stage. As a result, the piezoelectric discs are drivenwith a frequency corresponding with the resonant frequency of thetransducer. Thus, the horn length is shorter than λ/4. One exemplarytransducer has a main body length of 56 mm, a horn length of 28 mm, adisc diameter of 15.04 mm, a cylindrical horn section diameter of 16.25mm, an adapter (hammer) width of 12 mm, and an adapter (hammer) lateralextension width (or height) of 15 mm.

Operation of the transducer configuration shown in FIGS. 8 and 9 hasbeen shown to provide a number of optional resonance points betweenabout 20 kHz and about 1 MHz that may be selected as the operatingfrequency. The transducer has effectively transmitted ultrasonic energyat about 67.5 kHz, about 75 kHz, and about 77.5 kHz.

With reference now to FIG. 10, a drive circuit 240 is configured forcontrolling the transducer of FIGS. 8 and 9. The drive circuit 240 hasseveral features in common with the drive circuit described above andmay, in fact, be used to control the other transducers described herein.The drive circuit 240 is also generally configured as a full H-bridgedriver, albeit with different circuit elements. For instance, thecircuit 240 includes a bridge rectifier 242 to develop the high DCvoltage from which the drive signal is generated. An output of thebridge rectifier is also delivered to an AC-to-DC converter 244 forgeneration of a 15 Volt power supply, which, in turn, is fed to aregulator 246 that develops a 5 Volt power supply used by an oscillator248 and an inverter 250. The oscillator 248 establishes the frequency ofthe drive signal by passing its oscillating output to a pair offull-bridge drivers 252, either directly or indirectly through theinverter 250. Each driver 252 then sends switch control signals inaccordance with the oscillator frequency to a pair of switch circuits254, the terminals of which are connected across the transducer discs inthe full H-bridge configuration.

FIGS. 11A and 11B graphically depict the results of experiments thatshow the increases in energy transmission arising from the applicationof ultrasonic vibrations. With a curling iron configured as describedabove in connection with FIG. 1, the power transmission increased about14% when the ultrasonic vibrations were applied. With the flat iron ofFIG. 6, the power transmission increased at least about 10%. Theincreases were measured via a determination of the amount of energytransferred to a wet cloth. Specifically, the barrel (or flat plate) washeated to its maximum temperature setting with the ultrasonic transducerboth turned on and turned off. In each case, a wet cloth with a knownweight was applied to the barrel (or plate), and the iron was allowed toheat the cloth for five minutes. The cloth was then weighed to determinehow much water has been removed. From that determination, the amount ofenergy transferred to the cloth was calculated. The same curling (orflat) iron was used in each case so that thermal masses, maximumtemperatures, and other iron variables remained constant.

FIG. 12 shows an ultrasonic curling iron 260 constructed in accordancewith another exemplary embodiment. The curling iron 260 may be similarto the curling iron described above with the exception of the transducerand heating element locations. In this case, an ultrasonic transducer262 is disposed outside of a barrel 264. Even though the transducer 262is not housed within the barrel 264, the transducer 262 is againdisposed and oriented along the longitudinal axis of the barrel 264. Thetransducer 262 is secured to an exterior side 266 of an end cap 268 ofthe barrel 264 in any desired manner. As described above, the transducer262 may have a horn with a flat front face to maximize the surface areain contact with the exterior side 266 of the end cap 268. The transducer262 may be housed within an enclosure 270 coupled to the barrel 264 viaone or more fasteners, an adhesive layer, or any other attachmentmechanism. This alternative location for the transducer 262 may providedesign flexibility if, in fact, space within the barrel 264 is toolimited for a desired transducer configuration, size, geometry, etc. Thetransducer 262 is shown schematically in FIG. 12, and need not have theLangevin transducer configuration shown. Despite the alternativetransducer location, the vibration transmission path still passesthrough a styling surface 272 of the barrel 264.

One advantage of this exterior mounting of the embodiment of FIG. 12 isthat the heating element(s) may run the entire length of the barrel 264.With the transducer 262 not disposed within the barrel 264, thetransducer 262 does not block the extension of the heating elements. Asa result, the heating elements (or one end thereof) may be disposed ator near a distal end 274 of the barrel.

FIG. 13 depicts another alternative Langevin-based transducerconfiguration that does not rely on a lateral translation of thevibrations via a horn adapter. In this example, a transducer 280includes a substantially frustoconical horn stage 282 extending forwardfrom piezoelectric and reflector stages 284, 286. The horn stage 282 isgenerally shaped so that a contact interface with a plate 288 disposedalong the horn stage 282 is formed. To that end, the horn stage 282includes a pair of diametrically opposed flat surfaces 290, each ofwhich may have a parabolic outline. The surfaces 290 may lie in parallelplanes such that, when the transducer 280 is oriented axially along theplate 288, one of the surfaces 290 lies flat against a top side of theplate 288 to increase the contact surface area. To that end, an opening292 in a heating element 294 may provide access to the top side of theplate 288. In other cases, the opening 292 may be cut out to match theshape of the transducer surface.

Generally speaking, the material(s) from which the transducer hornsdescribed above are made are selected to ensure effective transmissionof the ultrasonic vibrations through the interface between the horn andthe barrel, plate, or other component. Effective transmission generallyavoids reflection at the interface, which may occur in situations wherethe impedance of the materials on either side of the interface do notsufficiently match. Suitable materials for the transmission ofultrasonic vibrations in the context of hairstyling devices includealuminum and duraluminum because the acoustic impedance of thesematerials is approximately halfway between (i.e., an average of) theacoustic impedances of the ceramic (PZT) discs (45 MRay) and the waterin the hair being styled (1.5 MRay), i.e., the final medium. Aluminumand duraluminum, for instance, have acoustic impedances of 17.3 MRay and17.6 MRay, respectively. Duraluminum may be preferable over aluminumbecause it is harder. Other materials may be used, including those thathave crystalline or polycrystalline material structures.

Notwithstanding the advantages of the foregoing examples, the transducermay be mounted in a variety of locations on the hairstyling devices. Forinstance, the transducer may be mounted on the clip or clamp of acurling iron. The transducers also need not be oriented axially, i.e.,along the longitudinal axis of barrel. Even when the transducer isoriented axially, the horn may be configured to transmit vibrations in adirection transverse to the longitudinal axis of the barrel. Thus, thevibrations may be transmitted through the barrel, plate, or otherhousing structure radially, longitudinally, laterally, or anycombination thereof. A variety of other translation sections other thanthe elbow-shaped adapter described above may be used to change thedirection of the vibrations. Each housing or styling surface may containor have more than one transducer associated therewith.

The transducers may be mounted on a flat surface extruded onto the innersurface of the above-described barrels or wands. The flat surface may besimilar to those formed for supporting heating elements. The transducersmay alternatively or additionally mounted to an end of the platesdescribed above for transmission of the vibration longitudinally.

The plate with which the transducer is contact in some of theabove-described embodiments may be floating relative to the wand or armhousing via one or more springs. The plate is indirectly coupled to thewand housing via the spring(s), in contrast to the plates describedabove which are rigidly fixed to the wand housing. The separation orindirect coupling of the plate and the wand housing may reduce theamount of vibration energy absorbed by, or dissipated via, the housing.

The above-described barrels, plates and other objects with which thetransducers are in contact may be sized to maximize wave transmissionwithin the plate or object. For instance, the plate or barrel may have alength or other dimension equal to the wavelength or a direct multiplethereof.

Other ultrasonic generators may be used. As described above, the deviceresponsible for generating the ultrasonic vibrations may be located atvarious positions, including those within the barrel, handle, arm, wand,or other hollow structure or housing, as well as those exterior to, butin contact with, such structures, as well as those in contact with someother element in contact with the hair, such as a clip or clamp. Thus,in some cases, the ultrasonic generator is not in direct contact withthe barrel or other iron structure.

The construction and configuration of the wands, arms, and elongatehousings of the devices described above may vary widely from theexamples shown. They need not be of uniform construction, circumference,diameter, or two-piece construction

The disclosed hairstyling devices are not limited to curling irons withclips or spring-loaded clamps. The ultrasonic vibrations may be appliedto the hair via clipless wands in which the hair is wrapped around a rodor styled using an iron with a Marcel handle.

A variety of horn shapes may be used with the disclosed hairstylingdevices. The transducer horns are not limited to cylindrical orfrustoconical shapes. In this way, the disclosed hairstyling devices mayaccommodate a wide range of barrel diameters and shapes. The disclosedhairstyling devices are also not limited to Langevin transducers orbolt-clamped transducer stacks. A variety of different piezoelectricarrangements may be used, such that the configuration and constructionof the sections, stages, or components may vary from the examples shownabove.

Although certain curling irons and flat irons have been described hereinin accordance with the teachings of the present disclosure, the scope ofcoverage of this disclosure is not limited thereto. On the contrary, allembodiments of the teachings of the disclosure that fairly fall withinthe scope of permissible equivalents are disclosed by implicationherein.

1. A device for styling hair comprising: a wand defining a handle gripsurface and a first styling surface spaced from the handle grip surface;a plate defining a second styling surface, the plate being pivotallycoupled to the wand to clamp the hair between the first styling surfaceand the second styling surface; a heating element in thermalcommunication with the first styling surface or the second stylingsurface to transfer heat to the hair via the first styling surface orthe second styling surface, respectively; and an ultrasonic transducerconfigured to generate ultrasonic vibrations, wherein the ultrasonictransducer includes a horn in contact with the wand or the plate totransmit the ultrasonic vibrations to the hair via the first stylingsurface or the second styling surface, respectively.
 2. The device ofclaim 1, wherein the wand is oriented along a longitudinal axis, andwherein the ultrasonic transducer is oriented along the longitudinalaxis such that the ultrasonic vibrations are generated in a directionparallel to the longitudinal axis.
 3. The device of claim 1, wherein theultrasonic transducer is disposed within the wand.
 4. The device ofclaim 3, wherein the ultrasonic transducer includes a horn with a rim incontact with an interior surface of the wand that defines an annularinterface through which the ultrasonic vibrations travel.
 5. The deviceof claim 1, wherein the wand includes a barrel that terminates at an endcap, wherein the plate is curved to match a curvature of the barrel, andwherein the ultrasonic transducer includes a horn in contact with theend cap.
 6. The device of claim 5, wherein the barrel has a length equalto a wavelength of the ultrasonic vibrations or a multiple of thewavelength.
 7. The device of claim 1, further comprising an armpivotally coupled to the wand, wherein the plate is mounted on the arm,and wherein the first and second styling surfaces are flat.
 8. Thedevice of claim 1, further comprising a flat plate mounted on the wand,the flat plate having a first side that defines the first stylingsurface and a second side in contact with the ultrasonic transducer. 9.The device of claim 8, wherein the ultrasonic transducer is oriented inalignment with the wand, and wherein the ultrasonic transducer includesa horn adapter to direct the ultrasonic vibrations laterally toward theflat plate.
 10. The device of claim 8, wherein the flat plate has alength equal to a wavelength of the ultrasonic vibrations or a multipleof the wavelength.
 11. The device of claim 1, wherein the wand includesa handle that defines the handle grip surface and further includes abarrel extending from the handle and defining the first styling surface.12. The device of claim 11, wherein the ultrasonic transducer isdisposed in contact with, and external to, the barrel.
 13. A device forstyling hair comprising: a first arm defining a first handle gripsurface; a second arm pivotally coupled to the first arm and defining asecond handle grip surface; a first flat plate mounted on the first armand defining a first styling surface spaced from the first handle gripsurface; a second flat plate mounted on the second arm and defining asecond styling surface spaced from the second handle grip surface, thefirst and second flat plates being positioned to clamp the hair betweenthe first and second styling surfaces; a heating element in thermalcommunication with the first flat plate or the second flat plate totransfer heat to the hair via the first styling surface or the secondstyling surface; and an ultrasonic transducer secured to the first armand configured to generate ultrasonic vibrations, wherein the ultrasonictransducer includes a horn in contact with the first flat plate totransmit the ultrasonic vibrations to the hair via the first stylingsurface.
 14. The device of claim 13, wherein the first arm is orientedalong a longitudinal axis, and wherein the ultrasonic transducer isoriented along the longitudinal axis such that the ultrasonic vibrationsare generated in a direction parallel to the longitudinal axis.
 15. Thedevice of claim 13, wherein the ultrasonic transducer is disposed withinthe first arm.
 16. The device of claim 13, wherein the ultrasonictransducer is oriented in alignment with the first arm, and wherein theultrasonic transducer includes a horn adapter to direct the ultrasonicvibrations laterally toward the first flat plate.
 17. The device ofclaim 13, wherein the first flat plate has a length equal to awavelength of the ultrasonic vibrations or a multiple of the wavelength.